compile scope expressions

bin/main.ml

@@ -5,7 +5,7 @@ let () =
   Logs.set_level (Some Logs.Debug);
 
   try
-    let ast = parse "val x = 3 val y = 5 val output = 2 * (if(9 < 8) x else 1 + y)" in
+    let ast = parse "val z = 5 val output = 1 + (({ val x = 3 val y = 4  x * y }) + z)" in
     let prog = compile ast in
     let ret = run prog in
     Fmt.pr "{\"program\":%a,\"output\":%a}" Code.pp_program prog Value.pp ret

lib/compile/bcc.ml

@@ -72,8 +72,9 @@ let compile modl =
         bb := jp;
         Reg tmp
     | Ast.Obj body -> compile_obj env body
+    | Ast.Scope body -> compile_scope env body
     | _ -> failwith "Bcc.compile_exp: TODO"
-  and compile_obj env items =
+  and compile_block env items =
     let self = !sp in
 
     (* construct new env and vtable *)
@@ -92,7 +93,7 @@ let compile modl =
     in
     let vtable = Value.{ elems; n_slots } in
 
-    (* emit constructor / field inits *)
+    (* emit constructor, compile val fields, and get result of final expression *)
     emit (CON (self, vtable));
     let emit_set name rhs =
       let slot = (Env.find name env).slot in
@@ -100,23 +101,33 @@ let compile modl =
       emit_mov (self + 1) (Code.cst_of_int slot);
       emit (SET (self, self + 1))
     in
-    List.iter
-      (function
-        | Ast.Item_fun (_, _, _) -> failwith "Bcc: unsupported: methods"
-        | Ast.Item_exp e ->
-            sp := self + 1;
-            ignore (compile_exp env e)
-        | Ast.Item_obj (name, body) ->
-            sp := self + 2;
-            emit_set name (compile_obj env body)
-        | Ast.Item_val (name, rhs) ->
-            sp := self + 2;
-            emit_set name (compile_exp env rhs))
-      items;
-
-    (* reset sp and return self *)
+    let final_exp =
+      List.fold_left
+        (fun _ -> function
+          | Ast.Item_fun (_, _, _) -> failwith "Bcc: unsupported: methods"
+          | Ast.Item_exp e ->
+              sp := self + 1;
+              Some (compile_exp env e)
+          | Ast.Item_obj (name, body) ->
+              sp := self + 2;
+              emit_set name (compile_obj env body);
+              None
+          | Ast.Item_val (name, rhs) ->
+              sp := self + 2;
+              emit_set name (compile_exp env rhs);
+              None)
+        None
+        items
+    in
+    self, final_exp
+  and compile_obj env items =
+    let self, _ = compile_block env items in
     sp := self + 1;
     Code.Reg self
+  and compile_scope env items =
+    match compile_block env items with
+    | _, None -> failwith "block must end with an expression"
+    | _, Some ret -> ret
   in
 
   let env = Env.empty in